1. Field of the Invention
The present invention relates to a dipping apparatus which can automatically dip miniature components such as chip type electronic components or radial lead electronic components, and more particularly, it relates to a supplying/discharging mechanism for the dipping apparatus.
2. Description of the Background Art
In general, a holding plate having a number of receiving holes is employed for efficiently applying electrodes to end portions of a number of chip components, as disclosed in Japanese Patent Publication No. 3-44404 (1991). This holding plate comprises a hard substrate, a thin flat plate portion which is formed at a central portion of the substrate and provided with a number of through holes, and a rubber-like elastic member which is embedded in a concave portion defined in the flat plate portion and provided with receiving holes passing through the elastic member, which are smaller in diameter than the through holes. The holding plate elastically holds chip components in the receiving holes to with parts of the components projecting and brings the projected portions downwardly into contact with an upper surface of a plate which is coated with a thin film of electrode paste such as silver paste, thereby uniformly applying electrodes onto the projecting end portions of the chip components.
A dipping apparatus can be employed for automatically dipping such chip components. For example, a conceivable dipping apparatus engages every holding plate which is supplied by a conveyor with chucking pawls and downwardly moves the chucking pawls for bringing projected portions of chip components, which are held by the holding plate, into contact with an upper surface of a plate coated with electrode paste. Then the apparatus upwardly moves the chucking pawls for transferring the holding plate to a take-out conveyor.
In such a dipping apparatus, it is necessary to transfer the holding plate from a take-in conveyor to the chucking pawls and from the chucking pawls to a take-out conveyor with no vibration. If any vibration occurs during such movement, the chip components which are partially projected from the lower surface of the holding plate may drop from or incline in the receiving holes. When the chip components are not more than 3.2 mm in length, for example, only portions not more than 2.0 mm in length are received in the receiving holes. Thus, the holding plate has extremely small holding power.
The holding plate may conceivably be transferred by different methods. In a first method, a take-in conveyor may be continuously provided under the chucking pawls. In this case, however, the chucking pawls or the holding plate which is held by the chucking pawls disadvantageously interferes with the conveyor when the same is vertically moved, and hence it is impossible to maintain the holding plate in a horizontal state.
In a second method, the holding plate may be carried by a conveyor to a position in front of the chucking pawls, so that the same is pushed by a direct-acting actuator such as a cylinder onto the chucking pawls. In this case, however, the holding plate may be vibrated by impact etc. which is caused upon transfer to the chucking pawls, such that the chip components may drop from the receiving holes or the direction of the holding plate may be slightly changed so as to cause deviation in the positional relation of the components with respect to the chucking pawls.
In a third method, a conveyor may be carried to a position in front of the chucking pawls, which in turn are slid onto the conveyor. When the chucking pawls are vertically moved and horizontally slid in such a manner, however, the mechanism is complicated and accuracy of the positions for vertically moving the chucking pawls is decreased. In order to apply a constant amount of electrode paste to the chip components and prevent the lower surface of the holding plate from adhesion of the electrode paste, extremely high accuracy is required for the positions when vertically moving the chucking pawls as well as for keeping them horizontal.